【発明の詳細な説明】[Detailed description of the invention]
本発明は、コークス炉ガスの湿式脱硫設備から
排出される脱硫廃液中のチオシアン酸塩を利用し
たチオシアン酸第一銅の製造方法に関する。
コークス炉ガス中には、通常数グラム／m3程度
の硫化水素、シアン化水素が含有されているの
で、それを除去（脱硫・脱シアンと称す）するた
めに、現在、有機触媒を含有させたアンモニヤな
いしナトリウムのようなアルカリ金属塩水溶液と
循環向流接触させる方法が採られ、タカハツクス
法ないしフマツクス法などとして稼動されてい
る。むろん工業的には循環液の一部は該循環系か
ら絶えず抜き去られ、それに見合つた量の液が補
給せられる。かく、脱硫設備から抜き去られた廃
液は脱硫廃液と称されているが、その中には多量
のチオシアン酸およびチオ硫酸が、上述した各種
アルカリ塩の形態で含有されており、かつ、ピク
リン酸とかキノンなど芳香族有機化合物に由来し
て暗褐色を呈している。第１表は、その典型例た
るアンモニヤベースの脱硫廃液の成分組成を示す
ものである。
The present invention relates to a method for producing cuprous thiocyanate using thiocyanate in desulfurization waste liquid discharged from coke oven gas wet desulfurization equipment. Coke oven gas usually contains about several grams/ m3 of hydrogen sulfide and hydrogen cyanide, so in order to remove it (referred to as desulfurization/desyanide), ammonia containing an organic catalyst is currently being used. A method of circulating countercurrent contact with an aqueous solution of an alkali metal salt such as sodium or sodium is employed, and is operated as the Takahakus method or the Fumakus method. Of course, in industrial practice, a portion of the circulating fluid is constantly removed from the circulating system, and a proportionate amount of fluid is replenished. Thus, the waste liquid extracted from the desulfurization equipment is called desulfurization waste liquid, but it contains a large amount of thiocyanic acid and thiosulfuric acid in the form of the various alkali salts mentioned above, and picric acid. Its dark brown color comes from aromatic organic compounds such as quinone. Table 1 shows the composition of an ammonia-based desulfurization waste solution, which is a typical example.
【表】
本発明者らは、このような脱硫廃液中に含有せ
られている有価物の回収について研究を行い、そ
のチオシアン酸塩を、船底塗料、防黴剤、銅メツ
キなどの用途を有し、とくに最近防汚剤（船底塗
料用顔料）として、従来の亜酸化銅に勝るとも劣
らないとされるチオシアン酸第一銅の製造方法を
完成した（特願昭54−34704号）。
その方法は脱色後の脱硫廃液に、該廃液が含有
するチオシアン酸と等モル以下で、チオ硫酸と等
モル以上の第二銅塩を添加反応させるものであ
る。しかし、この方法で合成取得したチオシアン
酸第一銅は、しばしば黒色ないし灰色もしくは青
色に着色して製品価値が低い場合があり、また粒
度が細かであるがために別に長時間を要するな
どの難点があつた。
本発明は上述した難点を改善すべく為されたも
のであつて、前述先行発明とは反対に活性炭で脱
色したあとの廃液を、PH４以下に調整した第二銅
塩水溶液中に添加反応せしめる方法である。
この方法によれば先行発明方法によるよりも、
チオシアン酸第一銅が過し易い粗大結晶として
得られるのみならずその色も白色ないし極く淡青
色で、直ちに市販することができる。
本発明方法において脱硫廃液を脱色するのに活
性炭を用いる理由は、他の各種脱色剤に比し、安
価かつ確実に脱色でき、しかもチオシアン酸第一
銅の収得量に悪影響を及ぼすことが少いからであ
る。もしも、脱色しないで脱硫廃液をそのまゝ直
接第二銅塩水溶液中に添加反応せしめようとすれ
ば、得られるチオシアン酸第一銅が濃赤色ないし
褐色に着色する不都合を生ずる。脱色のために脱
硫廃液中に添加する活性炭の量は、通常５〜20
ｇ／程度でよい。それは、本発明者が実験的に
求めた値である。
本発明の反応に関与する銅が、塩化第二銅、硫
酸銅のような塩化合物に限定せられる理由は、反
応速度の速いイオン反応となす関係で、水溶液と
して使用するがためである。したがつて水溶性の
低い酸化第二銅、水酸化第二銅、硫化銅などは排
除される。
本発明において、PH４以下に調整したCu2+水
溶液中に脱色後の脱硫廃液を添加反応させること
によつて、製品品質に好影響を携らす理由は必ず
しも明瞭ではないが、本発明者らは、一応次の通
り考える。即ち、先行発明では、脱色後の脱硫廃
液を反応容器に入れ、PHを整えたのち、撹拌下に
第二銅塩水溶液を徐々に添加するものであつて、
第二銅塩の添加量は、該廃液中のチオ硫酸のモル
数以上で、チオシアン酸のモル数以下である。そ
れは、少量のCu2+が多量のSCN-、S2O3 2-中に添
加されることを意味し、未反応のS2O3 2-が多量
に存在する状態でチオシアン酸第一銅が生成され
ることを意味する。この場合にはCu2+とS2O3 2-
とが錯体を形成し易いということのほか反応に際
して、粒径の増大を目的として種晶を添加する場
合、チオシアン酸第一銅が、チオ硫酸によつて溶
解（錯体を形成する）させられるため、種晶がそ
の効果を十分発揮し得ないことゝなる。これに対
し、本発明方法におけるように、第二銅塩水溶液
中に廃液を添加して行く場合には多量に存在する
Cu2+中に、廃液中のS2O3 2-が少量ずつ添加され
て行くために、この添加と同時的にS2O3 2-は
Cu2+によつて酸化され、ポリチオン酸や硫酸と
なる。換言すれば反応はS2O3 2+の実質上存在し
ない状態で進行することになる。したがつて
Cu2+とS2O3 2-の錯体形成による着色や、チオ硫
酸の分解による亜硫酸ガスの発生と遊離いおうの
生成、あるいは種晶の溶解などの現象が、ほゞ完
全に抑制され、着色の少い、しかも粒径の大きな
結晶としてチオシアン酸第一銅が生成するのであ
る。
なお、第二銅塩水溶液のPHを４以下に調整した
のち、脱色脱硫廃液を添加するのは、反応時のPH
が４以上では、液中に溶解銅が多量に残留し、
液の処理が必要となるためである。
実施例 １
容量1000mlのビーカに、水300mlを入れ、
CuSO4・5H2O0.096molを加えて溶解したのち、
PHスタツトを接続し、20％H2SO4および20％
NaOHを用いて、第２表実験条件の欄に所載し
たPH値に調整する。ついで撹拌しながら別に作製
しておいた種晶0.5ｇを加え、つぎに予じめ活性
炭で脱色しておいた脱硫廃液（SCN-1.35mol／
、S2O3 2-0.57mol／）100mlを、小型定量ポ
ンプを用いて2.5ml／分の速度で添加した。該廃
液添加完了後も引続き30分間撹拌を継続した。
生成したCuSCNを常法通り別水洗し、80℃
で３〜５時間乾燥したのち、該CuSCNの沈殿量
を測定し、また別途そのときの液中の溶解銅量
をも測定した。測定結果は第２表記載のとおりで
ある。[Table] The present inventors have conducted research on the recovery of valuable substances contained in such desulfurization waste liquid, and have used the resulting thiocyanate for applications such as ship bottom paint, antifungal agents, and copper plating. In particular, we have recently completed a method for producing cuprous thiocyanate, which is said to be as good as conventional cuprous oxide as an antifouling agent (pigment for ship bottom paint) (Japanese Patent Application No. 34704/1982). The method involves adding and reacting a cupric salt in an amount equal to or less than the thiocyanic acid contained in the desulfurized waste solution after decolorization, and a cupric salt in an amount equal to or more than the equimolar amount to the thiosulfuric acid contained in the waste solution. However, cuprous thiocyanate synthesized and obtained using this method is often colored black, gray, or blue and has low product value, and also has drawbacks such as requiring a long time due to the fine particle size. It was hot. The present invention has been made in order to improve the above-mentioned difficulties, and is a method in which, contrary to the above-mentioned prior invention, waste liquid after decolorization with activated carbon is added to a cupric salt aqueous solution adjusted to a pH of 4 or less and reacted. It is. According to this method, compared to the prior invention method,
Cuprous thiocyanate is not only obtained as coarse crystals that are easy to pass through, but also white to very pale blue in color, and can be immediately commercially available. The reason why activated carbon is used to decolorize the desulfurization waste liquid in the method of the present invention is that it can decolorize cheaply and reliably compared to other various decolorizing agents, and it has little negative effect on the yield of cuprous thiocyanate. It is from. If the desulfurization waste liquid is directly added to the cupric salt aqueous solution without decolorization, the resulting cuprous thiocyanate will be colored deep red to brown. The amount of activated carbon added to the desulfurization waste liquid for decolorization is usually 5 to 20%.
It may be about g/g. This is a value experimentally determined by the inventor. The reason why the copper involved in the reaction of the present invention is limited to salt compounds such as cupric chloride and copper sulfate is that it is used in the form of an aqueous solution in order to achieve a fast ionic reaction. Therefore, cupric oxide, cupric hydroxide, copper sulfide, etc., which have low water solubility, are excluded. In the present invention, the reason why product quality is positively affected by adding desulfurized waste liquid after decolorization to a Cu 2+ aqueous solution adjusted to PH4 or less is not clear, but the present inventors Let's think about it as follows. That is, in the prior invention, after the desulfurization waste liquid after decolorization is put into a reaction vessel and the pH is adjusted, a cupric salt aqueous solution is gradually added while stirring.
The amount of cupric salt added is greater than or equal to the number of moles of thiosulfuric acid and less than or equal to the number of moles of thiocyanic acid in the waste liquid. It means that a small amount of Cu 2+ is added into a large amount of SCN - , S 2 O 3 2- , and cuprous thiocyanate is added in the presence of a large amount of unreacted S 2 O 3 2- . means that it is generated. In this case Cu 2+ and S 2 O 3 2-
In addition to the fact that thiosulfuric acid easily forms complexes, when seed crystals are added for the purpose of increasing particle size during the reaction, cuprous thiocyanate is dissolved (forms a complex) by thiosulfuric acid. This means that the seed crystal cannot fully exhibit its effect. On the other hand, when the waste liquid is added to the cupric salt aqueous solution as in the method of the present invention, a large amount of
Because S 2 O 3 2- from the waste liquid is added little by little into Cu 2+ , S 2 O 3 2- is added at the same time as this addition.
Oxidized by Cu 2+ to polythionic acid and sulfuric acid. In other words, the reaction proceeds in the substantial absence of S 2 O 3 2+ . Therefore
Phenomena such as coloring due to complex formation between Cu 2+ and S 2 O 3 2- , generation of sulfur dioxide gas and free sulfur due to decomposition of thiosulfuric acid, and dissolution of seed crystals are almost completely suppressed, resulting in no coloration. Cuprous thiocyanate is produced as crystals with a small amount of particles and a large particle size. In addition, after adjusting the pH of the cupric salt aqueous solution to 4 or less, the decolorizing and desulfurizing waste liquid is added because the pH during the reaction is
When is 4 or more, a large amount of dissolved copper remains in the liquid,
This is because the liquid needs to be treated. Example 1 Put 300ml of water into a beaker with a capacity of 1000ml,
After adding and dissolving 0.096 mol of CuSO 4 5H 2 O,
Connect PH stat, 20% H2SO4 and 20%
Using NaOH, adjust the pH value to the value listed in the experimental conditions column of Table 2. Then, while stirring, add 0.5 g of seed crystals prepared separately, and then add the desulfurization waste liquid (SCN - 1.35 mol/
, S 2 O 3 2- 0.57 mol/) was added at a rate of 2.5 ml/min using a small metering pump. After the addition of the waste liquid was completed, stirring was continued for 30 minutes. The generated CuSCN was washed separately with water as usual and heated to 80℃.
After drying for 3 to 5 hours, the amount of CuSCN precipitated was measured, and the amount of dissolved copper in the solution at that time was also separately measured. The measurement results are shown in Table 2.
【表】
第２表に示されるとおり、合成時のPHは4.0以
下なかんずく2.0以下が好ましい。なお、得られ
たCuSCN結晶は、平均粒径1.4μで白色、純度99
％以上で、そのまゝ市販可能であつた。また、予
じめ活性炭処理をしておかなかつた廃液について
同条件で生成させた沈殿物は、平均粒径1.0μで濃
赤色ないし濃褐色、純度97％、収率99％であつ
た。
なお、CuSCN結晶の平均粒径は、光透過式粒
度分布測定装置で測定し重量平均で示した。
実施例 ２
容量1000mlのビーカ４個に、それぞれ水を入
れ、これにCuSO4・5H2O0.096molを加え溶解し
て400mlとなし、PHスタツトを接続し、20％
H2SO4および20％NaOHによりPHを2.0一定に保
持したまま、別に作製しておいた種晶0.5ｇを加
え、ついで、メスシリンダに採取しておいた実施
例１の脱色後の脱硫廃液の所定量（第３表実験条
件欄）を、小型定量ポンプを用いて2.5ml／分の
速度で添加し、添加完了後もさらに30分撹拌を継
続した。
こゝに生成したCuSCNを、常法通り別水洗
し、80℃で３〜５時間乾燥したのち、その重量つ
まり沈殿量を秤量し、またその時の液中の溶解
銅量をも分析した。それら結果は第３表に表示し
た通りである。[Table] As shown in Table 2, the pH during synthesis is preferably 4.0 or less, especially 2.0 or less. The CuSCN crystals obtained were white with an average particle size of 1.4μ, and a purity of 99%.
% or more, it could be marketed as is. Further, the precipitate produced under the same conditions from the waste liquid that had not been treated with activated carbon in advance was dark red to dark brown, with an average particle size of 1.0 μm, a purity of 97%, and a yield of 99%. Note that the average particle size of the CuSCN crystals was measured using a light transmission type particle size distribution analyzer and expressed as a weight average. Example 2 Fill 4 beakers with a capacity of 1000 ml with water, add and dissolve 0.096 mol of CuSO 4 5H 2 O to make 400 ml, connect a PH stat, and add 20%
While keeping the pH constant at 2.0 with H 2 SO 4 and 20% NaOH, 0.5 g of seed crystals prepared separately was added, and then the desulfurization waste liquid after decolorization of Example 1 was collected in a measuring cylinder. A predetermined amount of (Experimental conditions column in Table 3) was added at a rate of 2.5 ml/min using a small metering pump, and stirring was continued for an additional 30 minutes after the addition was completed. The CuSCN thus produced was washed separately with water as usual, dried at 80°C for 3 to 5 hours, and then its weight, ie, the amount of precipitate, was weighed, and the amount of dissolved copper in the solution at that time was also analyzed. The results are shown in Table 3.
【表】
この表から判るように、反応時のSCN-と銅と
のモル比は1.3望ましくは1.4とするのが適当とさ
れる。なお、こゝに秤量したチオシアン酸銅は、
純度99.5％以上、平均粒径1.3μ、色は白色で、そ
のまゝ市販可能な良質なものであつた。
比較例
容量1.0のビーカに実施例１記載の脱色後の
脱硫廃液100mlを採り、PHスタツトを接続し、20
％H2SO4および20％NaOHを用いてPH6.0（PH5.0
以下では廃液中のS2O3 2-が分解するからである）
としたのち、あらかじめ水300mlに溶解した
CuSO4・5H2O0.096molを、撹拌下に小型定量ポ
ンプにより7.5ml／分の割合で添加した。添加完
了後もさらに30分撹拌を継続し、その後生成した
CuSCNの沈殿は、これを常法通り別水洗し、
80℃で３〜５時間乾燥した。
こゝに生成したCuSCNは粒子が微細（平均粒
径0.9μ）で前記別が困難であつただけでなく、
青色に着色していて商品価値の乏しいものであつ
た。
本発明は上述の通り構成せられるからCOD値
数万〜十数万ppmという廃棄処分に苦慮する脱硫
廃液から、容易に良質なチオシアン酸第一銅が回
収できたのである。[Table] As can be seen from this table, it is appropriate that the molar ratio of SCN - to copper during the reaction is 1.3, preferably 1.4. In addition, the copper thiocyanate weighed here is
It had a purity of 99.5% or more, an average particle size of 1.3μ, and a white color, and was of good quality and could be sold as is. Comparative example: Pour 100ml of the desulfurization waste liquid after decolorization described in Example 1 into a beaker with a capacity of 1.0, connect a PH stat,
PH6.0 using % H2SO4 and 20% NaOH ( PH5.0
This is because S 2 O 3 2- in the waste liquid decomposes below)
After that, it was dissolved in 300ml of water in advance.
0.096 mol of CuSO 4 .5H 2 O was added at a rate of 7.5 ml/min with stirring using a small metering pump. After the addition was complete, stirring was continued for an additional 30 minutes, after which the formed
To precipitate CuSCN, wash it separately with water as usual,
It was dried at 80°C for 3 to 5 hours. The CuSCN produced here not only had fine particles (average particle size 0.9μ) and was difficult to separate as described above, but also
It was colored blue and had little commercial value. Since the present invention is configured as described above, high-quality cuprous thiocyanate can be easily recovered from desulfurization waste liquid with a COD value of tens of thousands to hundreds of thousands of ppm, which is difficult to dispose of.